Distance from human dwellings differentially affects the efficacy of a synthetic cattle urine odour lure to trap malaria vectors

BACKGROUND: Cost–effective outdoor–based devices for surveillance and control of outdoor mosquito vector populations can substantially improve their efficacy when baited with synthetic human and animal odours. This study aimed at assessing the dose–dependent efficacy of a previously developed synthetic cattle urine odour to lure malaria vectors, and other mosquito species, to traps placed at different distances from human dwellings outdoors. METHODS: The efficacy of the cattle urine odour lure was assessed through a 5 × 5 Latin square design, using two sets of 5 Suna traps placed at either 1.5 m or 5 m from an adjacent human dwelling, in the rural village of Sagamaganga, Tanzania. Each trap was deployed with one of four doses of the synthetic cattle urine odour blend or a solvent control (heptane). Traps were rotated daily so that each dose and control visited each position twice over a period of 20 experimental nights. The relative attractiveness of each treatment dose and control was compared using a generalized linear mixed model for each species caught. RESULTS: A total of 1568 mosquitoes were caught, of which 783 were anophelines and 785 were culicines. Of the anophelines, 41.6 and 58.3% were primary and secondary vector species, respectively. Unfed and fed females of the primary vector, Anopheles arabiensis, were caught dose–dependently, close to human dwellings (1.5 m), whereas unfed, fed and gravid secondary vector Anopheles pharoensis females were caught dose–dependently, but at a farther distance from the dwellings (5 m). Females of Culex spp. were caught dose–dependently in similar numbers irrespective of the distance from human dwellings. CONCLUSIONS: This study further clarifies the factors to be considered for the implementation of outdoor trapping using the synthetic cattle urine lure to target exophilic and exophagic malaria vectors, for which efficient surveillance and control tools are currently lacking. The findings resulting from this study make significant progress in providing the needed information to overcome the regulatory obstacles to make this tool available for integrated vector management programs, including registration, as well as evaluation and regulation by the World Health Organization.